1. Field of the Invention
The present invention relates to an image display apparatus, method, and program. More particularly, the present invention relates to an image display apparatus, method, and program capable of preventing a decrease in the maximum expansion rate by shortening the timing of reading from a memory and outputting an image to be expanded by an electronic zoom function.
2. Description of the Related Art
To date, an imaging apparatus for converting an image into an electronic signal, such as a video camera, for example, is additionally provided with a function of camera shake compensation, electronic zooming, etc.
Here, camera shake compensation is to obtain camera-shake information of the cameraman of a video camera by a gyro-sensor, etc., to cut out a portion of an image on the basis of the information, and to perform interpolation processing on the pixel values using adjacent pixel values in order to electronically expand or shrink the cut-out portion to an image of a standard angle of view. Also, electronic zooming is to cut out a portion of an image, and to perform interpolation processing on the pixel values using adjacent pixel values in order to electronically expand the cut-out portion to an image of a standard angle of view.
FIG. 1 is an example of a timing chart showing the address transition of an image memory for consecutive three screens and the input/output timing of images at full-screen display time in a known image display apparatus.
FIG. 1 shows a state of converting the resolution from an input image of horizontal 1920 pixels×vertical 540 lines into an output image of horizontal 1440 pixels×vertical 540 lines.
The image memory includes a ring buffer, the writing of data into the image memory is denoted by broken lines, and the reading of the written data is denoted by solid lines. The image memory is, for example, a memory in which the image obtained by converting the number of pixels of an input image in the lateral direction is written. The image written in the image memory is read from the image memory, then is appropriately subjected to the conversion of the number of lines in the vertical direction, and the obtained image is output as an output image.
The address of the image memory starts from 0, and the write address of the next line is obtained by incrementing for one line for each writing of one line. When the address reaches the end of the image memory, the write address of the next line is returned to 0 as shown in the figure, and then the write address is continued to be incremented for one line for each writing of one line again. The address to be the location of writing data is held after the completion of the processing for one screen, and the processing (writing) of the next screen is continued from the held address.
An input synchronization signal and an output synchronization signal are produced in synchronism with each other. While an image is being written into the image memory, the image of 1V before that image being written is read from the image memory. That is to say, for example, the image 1 written in the image memory during the period (t11 to t12) is subjected to the resolution conversion and read from the image memory during the period (t13 to t14) with a delay of 1V. During the period (t13 to t14), the writing of the image 2 of the next screen is carried out simultaneously. In the same manner, the image 2, which is one screen before the image 3, is read simultaneously with the writing of the image 3 during the period (t15 to t16).
FIG. 2 is a diagram illustrating the state in which the central part of the screen of an input image including horizontal 1920 pixels×vertical 540 lines, that is to say, a part including horizontal 1600 pixels×vertical 450 lines is specified for an effective range, and is resolution converted into an output image including horizontal 1440 pixels×vertical 540 lines as an example of the operation for the sake of camera shake compensation in a known image display apparatus.
Also, FIG. 3 shows the address transition of the image memory and the input/output timing of the image when the effective range is changed in sequence from horizontal 1600 pixels×vertical 450 lines (upper part of the screen), horizontal 960 pixels×vertical 270 lines (central part of the screen), and horizontal 1600 pixels×vertical 450 lines (lower part of the screen) as another example of the operation for the sake of camera shake compensation in a known image display apparatus.
In the examples of the operations in FIGS. 2 and 3, similarly as the example of the operation in FIG. 1, the input synchronization signal and the output synchronization signal are produced in synchronism with each other. While an image is being written into the image memory, the image of 1V before that image is read from the image memory. In these examples, although the writing period of an input image changes corresponding to the line position of the effective-range image, the reading period is the same, and the images are always output at constant output timing.